Process of making hydrosulfites.



UNITED STATES PATENT OFFICE.

MAX BAZLEN, OF LUDVVIGSHAFEN, GERMANY, ASSIGNOR TO THE BADISOHE ANILIN &SODA FABRIK, OF LUDWIGSHAFEN, GERMANY, A CORPORA- TION O F GERMANY.

PROCESS OF MAKING HYDROSULFITES.

SPECIFICATION forming part of Letters Patent N 0. 692,760, datedFebruary 4, 1902.

Application filed December 20, 1899. Serial No. 740,986- (No specimens.)

T ctZZ whom it may concern.-

Be it known that 1, MAX BAZLEN, doctor of philosophy, a subject of theKing of Wiirtemberg, residing at Ludwigshafen-on-the-Rhine,

in the Kingdom of Bavaria, Germany, have in-.

vented new and useful Improvements in Processes of PreparingHydrosulfites, of which the following is a specification.

I have invented a new general process for ID the production ofhydrosulfites, and by the aid of my new process I can produce solutionsof hydrosulfites more concentrated and freer from impurities than anysolutions of hydrosulfites hitherto known. This new solution [5constitutes a new and valuable article of commerce. Again, by a furtherstep I obtain new solid alkaline and other hydrosulfites, which are alsoof great value in the art.

In the present application for patent I vde- 2o sire to claim my newgeneral process for the manufacture of hydrosulfites, and I do not claimthe new solid hydrosulfites nor the new solutions which constitute,respectively, the subject-matter of separate applications for LettersPatent, Serial Nos. 740,987 and 740,988,

of even date herewith.

Technical sodium hydrosulfite, which is used for the reduction of indigofor the purpose of dyeing therewith, has hitherto generally beenprepared by adding zinc-dust to a solution of sodium bisulfite,preferably while keeping the solution cool, and subsequently removingthe zinc compound from the 'solution by means of lime. When this processis adopted, only about one-half of the sulfurous acid and ofthe sodiumcontained in the bisulfite is converted into the hydrosulfurousacidsalt. The remainder remains unused probably in the form of the sulfitesof sodium 0 and zinc. Grossman has described a process for using up to agreater extent this unused sulfite,whioh consistsin adding mineralacids, particularly sulfuric acid, so that some of' the sulfurous acidof the unconverted snlfite is set free and then by the further additionof zinc-dust the reduction is repeated. This process is described in thespecification of the German Patent No. 84,507, and when workingaccording to this specification about onethird more hydrosulfite can beobtained than can be obtained in the usual way; but the solution is lessconcentrated than the usual hydrosulfite solution, and it contains aconsiderable quantity of sulfates as an impurity.

I have devised a process by which it is possible not only to'obtain pureand, when desired, highly-concentrated solutions of hydrosulfite, butalso to convert practically the whole quantity of the bisulfite usedinto the corresponding'hydrosulfite. My said process for the productionof the hydrosulfite solution is based on the addition of free sulfurousacid to the bisulfite employed. The sulfurous acid may either be addedin aqueous solution or it maybe introduced in the form of gas. To obtainthe best result according to this invention, the quantity of sulfurousacid added in either way is arranged to be one-half the total quantityotherwise contained in the bisulfite used. The solution thus obtained isthen reduced with zinc-dust and treated with milk of lime. By workingaccording to my new process not only is the entire quantity of alkali inthe bisulfite fully used by being combined after the treatment with limewith the hydrosulfurous acid, but the formation of other salts asimpurities is prevented, and the resulting solutions are, if desired, soconcentrated and pure that it is possible to obtain from them solid and,as compared with any product hitherto prepared, very pure hydrosulfiteby evaporation in vacuo. The solid hydrosulfite can better be obtainedfrom this solution by separating it by means of common salt. organicbodies a method hitherto used in the arts only for organic bodies.

The following examples will serve to further illustrate the nature ofthe invention and the manner in which it can best be carried into 90' Ithus employ for the separation of insaid density about fifty-one (51)liters of Water and pass gaseous sulfurous acid through the solutionuntil the weight has been increased by about three and a quarterkilograms. Then add slowly about four and onefifth (42 kilograms ofzinc-dust. During this addition keep the solution at a temperaturebetween 30 and 40 centigrade by suitably cooling. When all the zinc-dusthas been added, stir for some time and then allow the mixture to standfor an hour or two. Next treat the liquid with milk of lime preparedfrom about four and one-fifth (4%) kilograms of quicklime and twenty(20) liters of water. Stir well, and finally allow the mixture to standfor at least six hours more. Then filter through a filter-press.

From the above mentioned quantity of twenty-five kilograms of sodiumbisulfite of 40 Baum according to the usual process hitherto practicedsufficient hydrosulfite results to reduce rather less than fivekilograms of indigo in the vat, while when working according to thisexample about eighty kilograms of sodium-hydrosulfite solution,possessing a density of about 11 Baum, are obtained, which aresufficient to reduce twice the aforesaid quantity of indigo toindigowhite in the vat.

Example 2: In order to produce a highlyconcentrated hydrosulfitesolution, mix together about twenty-eight and four-fifths 28%) kilogramsof sodium bisulfite of about 40 Baum density and thirty-four and onehalf(34%) kilograms of concentrated aqueous solution of sulfur dioxid,(containing about ten per cent. 80 or prepare a similar solution bydiluting the sodium-bisulfite solution with about thirty-one (31) litersof water and causing it to absorb the corresponding quantity of gaseoussulfur dioxid. To the solution obtained in either of the ways describedadd gradually about four and four-fifths (4 kilograms of zinc-dust, asdescribed in the foregoing example. Precipitate the zinc oxid with milkof lime prepared from four and four-fifths (41-) parts of quicklime andsixteen (16) liters 01: water and filter.

WVhen proceeding as hereinbefore described, one obtains a solution ofthe neutral sodium hydrosulfite, of which ten kilos are sufficient toreduce just under two kilograms of one hundred per cent. indigo. Thequantities and strengths of the solutions given in this example are socalculated that the quantity of alkali present in the sodium bisulfiteis after the reduction equivalent to the quantity of hydrosulturous acidformed, so that neutral sodium hydrosulfite is obtained. Of course ifthe concentration of any of the solutions employed be variedcorrespondingalterations must be made in the quantities or strengths ofthe other ingredients in order to obtain the best results.

In the foregoing examples I have described the use of sodium bisulfite.Instead of this, however, I may use an equivalent quantity of any otherbisulfite, such as potassium, ammonium, calcium, or chrome bisulfite.

Now what I claim is 1. The process for the manufacture of hydrosulfiteswhich consists in adding directly sulfurous acid as such to acommercially-pure bisulfite and reducing the mixture so obtained.

2. lhe process for the production of hydrosulfites consisting in addingto the bisulfite used a quantity of sulfurous acid equal to one-half thesulfurous acid otherwise contained in the said bisulfite and reducingthis mixture with zinc-dust.

3. The process for the production of hydrosulfites consisting in addingto the bisultite used a quantity of sulfurous acid equal to one-half thesulfurous acid otherwise contained in the said bisulfite and reducingthis mixture with zinc-dust and treating the resulting liquid with milkof lime.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

MAX BAZLEI \Vitnesses:

ERNEST F. EHRHARDT, JULIUS ABEL.

